Semiconductor device with lead frame having lead terminals with wide portions of trapezoidal cross section

ABSTRACT

A semiconductor device in which a semiconductor chip, a lead frame and metal wires for electrically connecting the lead frame are sealed with sealing resin. The lead frame has a plurality of lead terminal portions, a supporting portion for supporting the semiconductor chip, and hanging lead portions supporting the supporting portion. Each of the lead terminal portions adjacent to the hanging lead portion is a chamfered lead terminal portion having, at its head, a chamfered portion formed substantially in parallel with the hanging lead portion so as to avoid interference with the hanging lead portion.

This is a Divisional of U.S. application Ser. No.: 09/970,056, filedOct. 4, 2001 now U.S. Pat. No. 6,710,431.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resin-sealed type semiconductordevice, and especially to a one-side resin-sealed type semiconductordevice in which a surface of a lead frame on which a semiconductorelement is mounted is sealed with a resin and a lead frame usedtherefor.

2. Description of Related Art

Resin-sealed type semiconductor devices each provided with a lead framefor electrically connecting electrodes of the semiconductor to an outerwiring and the like are widely used. In such a semiconductor device, alead frame generally comprises a supporting portion for mounting asemiconductor element thereon, hanging lead portions for supporting thesupporting portion, and lead terminal portions for connecting metalwires thereto. A lead frame used in the process of fabricatingsemiconductors includes a plurality of unit regions corresponding to aplurality of semiconductor devices so that the plurality ofsemiconductor devices can be fabricated at the same time. One unitregion has a substantially rectangular shape. Each of the hanging leadportions extends inwardly from a corner portion of this rectangle, andin many cases, the lead terminal portions extend inwardly from sideparts of the unit region.

FIG. 5 is an enlarged schematic pan view showing a part in the vicinityof a corner of a unit region.

In the central part of the substantially rectangular unit region (in thedirection of arrow G), a supporting portion 51 is disposed. A hanginglead portion 52 extends from the supporting portion 51 toward the cornerportion. In the side parts of the unit region, substantially rectangularlead terminal portions 53 are provided. Base end portions of the leadterminal portions 53 are connected to a peripheral frame part 50. Thelongitudinal direction of the hanging lead portion 52 and thelongitudinal direction of the lead terminal portion 53 makes an angle ofsubstantially 45°.

In a lead frame, a plurality of unit regions each having such astructure are arranged and connected to the frame part 50. In theprocess of fabricating semiconductor devices, a lead frame is sealedwith a sealing resin in such a manner that the bottom surface of thelead terminal portion 53 is exposed. Thereafter, each unit of lead frameis cut along a cutting line M shown in broken line, and the cut end faceis substantially in the same plane with the side surface of the sealingresin.

In order to obtain a small-sized semiconductor device, it is preferablethat the length of the lead terminal portion 53 is as short as possible.However, since the lead terminal portion 53 functions as a lead forconnection with outer wiring substrate, the lead terminal portion 53needs to have a length (area) more than a predetermined length (area).From these reasons, the lead terminal portion 53 is formed to have apredetermined necessary minimum length L1.

The minimum distance between the hanging lead portion 53 and the leadterminal portion 53A adjacent to the hanging lead portion 53 must belarge enough to ensure insulating reliability between them. However, inorder to obtain a small-sized semiconductor device, it is preferablethat the minimum distance between them is small. From these reasons, theminimum distance between them is designed to be a predeterminednecessary minimum distance L2.

However, since the predetermined length L1 and the predetermine distanceL2 are required to be secured, miniaturization of mounting area of asemiconductor device is limited.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor devicein which each lead terminal portion has a length (area) necessary forouter connection and at has a length (area) necessary for outerconnection and at the same time insulating reliability between thehanging lead portions and lead terminal portions is secured, and a leadframe used for the semiconductor device.

Another object of the present invention is to provide a semiconductordevice having a small mounting area, and a lead frame used for thesemiconductor device.

A semiconductor device according to the present invention comprises asemiconductor chip having electrodes on the surface thereof, a leadframe having a plurality of lead terminal portions for electricconnection and a plurality of hanging lead portions each extendingobliquely with respect to the lead terminal portions and supporting asupporting portion on which the semiconductor chip is mounted, metalwires for connecting the lead terminal portions and the electrodes ofthe semiconductor device, and a sealing resin for sealing thesemiconductor element, the lead frame and the metal wires in such amanner that a part of each lead terminal portion is exposed. Theplurality of lead terminal portions include chamfered lead terminalportions each having, at its head, a chamfered portion formedsubstantially in parallel with the hanging lead portion so as to avoidinterference with the hanging lead portion.

Further, a lead frame according to the present invention comprises aplurality of lead terminal portions for electric connection and aplurality of hanging lead portions each extending obliquely with respectto the lead terminal portions and supporting a supporting portion onwhich the semiconductor chip is mounted. The plurality of lead terminalportions include chamfered lead terminal portions each having, at itshead, a chamfered portion formed substantially in parallel with thehanging lead portion so as to avoid interference with the hanging leadportion.

According to this invention, the lead terminal portions are chamferedsubstantially in parallel with the hanging lead portion so as to avoidinterference with the hanging lead portions. Accordingly, even if thechamfered lead terminal portion is disposed nearer to the hanging leadportion in comparison with the case of the conventional lead terminalportion, a distance more than a predetermined distance can still besecured between the lead terminal portion and the hanging lead portion.

That is, in a conventional lead frame, a lead terminal portion has acorner portion protruding toward a hanging lead portion. Therefore, ithas been necessary to dispose the lead terminal portion substantially onthe peripheral part side in order to avoid interference between an edgeof the corner portion and the hanging lead portion and secure a distancemore than a predetermined value therebetween. As a result, a unit regionin a lead frame corresponding to a semiconductor becomes large, and thesize in the plane direction of a semiconductor device using this unitregion becomes large.

On the contrary, according to the present invention, the lead terminalportion has a chamfered portion at its head and is opposed to thehanging lead portion at this chamfered portion. Therefore, the hanginglead portion can be disposed at a more inner portion in comparison withthe case of the conventional structure. Accordingly, a unit region oflead frame can be small-sized. As a result, the size in the planedirection of a semiconductor device can be reduced and the mounting areaof the same can be also reduced.

The chamfered portion is preferably comprises a linear side in parallelwith the lateral side of the hanging lead portion. However, other shapesare similarly effective as long as the portion is chamfered so as toavoid interference by the hanging lead portion. For example, thechamfered portion may comprise a curved side. Further, in the chamferedportion, the oblique side may extend through only a part or the wholewidth of the lead terminal portion.

It is preferable that the abovementioned chamfered lead terminal portionis disposed adjacent to the hanging lead portion.

Not only the lead terminal portion adjacent to the hanging lead portionbut also another lead terminal portion adjacent to this chamfered leadterminal portion may be a chamfered lead terminal portion. However, inthis case, the chamfered lead terminal portion adjacent to the hanginglead portion becomes shorter than the other chamfered lead terminalportions. Therefore, it is preferable that only lead terminal portionsadjacent to the hanging lead portion have such a chamfered portion. Inthis case, there is no remarkably short lead terminal portion.Therefore, in a semiconductor device using such a lead frame, all thelead terminal portions can be suitably connected to metal wires and anouter wiring substrate.

When only each lead terminal portion adjacent to the hanging leadportion comprises a chamfered lead terminal portion, the chamferedportion preferably has an oblique side extending throughout the wholewidth of the lead terminal portion. Thereby a unit region of lead framecan be minimized and the size of a semiconductor device using the samecan be minimized in plan view.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing a unit region of lead frameaccording to an embodiment of the present invention.

FIG. 2 is an enlarged schematic plan view showing a part in the vicinityof a corner of the unit region of lead frame shown in FIG. 1.

FIG. 3A is a sectional view along a cutting line C-C in FIG. 2, and FIG.3B is a sectional view along a cutting line D-D in FIG. 2.

FIG. 4 is a schematic sectional view of a resin-sealed typesemiconductor device fabricated using the lead frame shown in FIG. 1.

FIG. 5 is an enlarged schematic plan view showing a part in the vicinityof a corner of a conventional lead frame.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic plan view showing a unit region (a repetition unitcorresponding to a semiconductor device) of a lead frame 1 according toan embodiment of the present invention. The unit region of the leadframe 1 is, for example, substantially in the shape of a square andsubstantially symmetrical in the vertical and horizontal directions inFIG. 1. Therefore, reference numerals are given to only the upper leftquarter part of the unit region in FIG. 1, but each of the remainingquarter parts has the same shape. The unit region comprises a frameportion 2 disposed in the peripheral part, a supporting portion 4 in thecentral part, a hanging lead portion 3 connecting the supporting portion4 and an inner corner portion of the frame portion 2, and lead terminalportions 5 disposed on the inner side of the frame portion 2, andextending in parallel in the vertical and horizontal directions on thehorizontal and verticals sides, respectively. The frame portion 2 isusually provided with holes (not shown) for positioning, fixing and thelike the lead frame 1 in the fabricating process of a semiconductordevice.

The supporting portion 4 extends diagonally from the inner corner of theframe portion 2 through the hanging lead portion 3. In other words, thewhole of the supporting portion 4 is X-shaped. The supporting portion 4is larger in width than the hanging lead portion 3. A step 3 a isprovided in the way of the hanging lead portion 3, and the supportingportion 4 is upset in a higher position than that of the frame portion2.

The lead terminal portions 5 extend from the inner sides of the frameportion 2 toward the center thereof and vertically with respect to theinner sides. The hanging lead portion 3 is oblique with respect to thelongitudinal direction of the lead terminal portions 5 with an angle ofabout 45° in plan view. Each of the lead terminal portions 5 has thesame length.

A plurality of such unit regions each having the abovementionedstructure are disposed in close to one another and constitute a leadframe.

In the process of fabricating a semiconductor device, a semiconductorchip is die-bonded on the supporting portion 4, and electrodes of thesemiconductor chip and the lead terminal portions 5 are connected toeach other by metal wires. Thereafter, the semiconductor chip, thesupporting portion 4, a part of the hanging lead portion 3 and a part ofthe lead terminal portions 5 are covered with a sealing resin and thelead terminal portions 5 and the hanging lead portions 3 are cut at theposition of a cutting line E shown in a broken line. The region coveredwith the sealing resin is a region enclosed by the cutting line E.

FIG. 2 is an enlarged schematic plan view showing a corner part of aunit region of lead frame shown in FIG. 1.

Among the plurality of lead terminal portions 5, each lead terminalportion 5B not adjacent to the hanging lead portion 3 has a head sideformed perpendicular to the length thereof. On the other hand, each leadterminal portion 5A adjacent to the hanging lead portion 3 has anoblique head side substantially in parallel with and opposed to thesides of the hanging lead portion 3 through the whole width of the leadterminal portion 5A. In other words, the lead terminal portion 5A is achamfered lead terminal portion having, at its head end, a chamferedportion formed substantially in parallel with the hanging lead portion 3so as to avoid interference with the hanging lead portion 3.

Step portions are provided at the sides of each lead terminal portion 5.That is, the lead terminal portion 5 has two wide portions and twonarrow portions alternately disposed at shifted positions in thelongitudinal direction thereof. As can be seen in FIG. 2 with respect tothe adjacent lead terminal portions 5A and 5B, and is also apparent inFIG. 1 with respect to all adjacent terminal portions 5, the wide andnarrow portions of each adjacent pair of lead terminal portions (such asthe adjacent wide portions at the head ends of the lead terminalportions 5A and 5B) have respective opposing (adjacent) sides which areparallel to each other. The two wide portions and one narrow portion arewholly sealed within the sealing resin, and the remaining narrow portionis partly sealed with the sealing resin. With such a shape, the leadterminal portion 5 is hard to be pulled out toward the peripheral side.

FIG. 3A is a sectional view along the cutting line C-C of FIG. 2 andFIG. 3B is a sectional view along the cutting line D-D of FIG. 2.

The section along the cutting line C-C is a section of the wide portionof the lead terminal portion 5, and is in the shape of an invertedtrapezoid the upper side of which has a length t1 and the lower side ofwhich has a length t2 (t1>t2) (FIG. 3A).

The section along the cutting line D-D is a section of the narrowportion of the lead terminal portion 5, and is in the shape of arectangle having a width t2 (FIG. 3B) That is, the upper surface of thelead terminal portion 5 has different two widths t1 and t2 shifted inthe longitudinal direction, but the bottom surface thereof has the fixedwidth t2.

After sealing the lead frame 1 with a sealing resin, the sealing resinis filled to the position F in the same plane with the bottom surface ofthe lead terminal portion 5, and the bottom surface of the lead terminalportion 5 is exposed from the sealing resin to form a terminal portionfor outer connection (an outer lead portion). At the wide portion havingan inverted trapezoidal section (FIG. 3A), the lead terminal portion 5is wider in the sealing resin and has tapered surfaces opposed to thebottom surface side of the sealing resin. With this structure, the leadterminal portion 5 is hard to be pulled out downwardly from the sealingresin.

Further description will be given with reference to FIG. 2 again.

Since the lead terminal portion 5 functions as a lead for connectionwith outer wiring substrate, the exposed area of the lead terminalportion 5 from the sealing resin must be lager than a predeterminedarea. Therefore, it is necessary to secure more than a predeterminedlength of the lead terminal portion 5 after being cut. On the otherhand, in order to obtain a small-sized semiconductor device, it ispreferable that the length of the lead terminal portion 5 is as short aspossible. From these reasons, the lead terminal portion 5 is formed tohave a predetermined necessary minimum length L1.

The minimum distance between the hanging lead portion 3 and the leadterminal portion 5A adjacent to the hanging lead portion 3 must be largeenough to ensure insulating reliability between them. However, in orderto obtain a small-sized semiconductor device, it is preferable that theminimum distance between them is small. From these reasons, the minimumdistance between them is designed to be a predetermined necessaryminimum distance L2.

When, using a lead terminal portion 53 having a conventional shape shownin FIG. 5, the length of the lead terminal portion 53 is set to be thepredetermined length L1 and the minimum distance between the hanginglead portion 52 and the adjacent lead terminal portion 53 is set to bethe predetermined distance L2, the lead terminal portion 53 must bedisposed further on the peripheral portion side in comparison with thecase of this embodiment. The reason is that, since a corner portion 54of a conventional lead terminal portion 53 at the most adjacent positionto the hanging lead portion 52 protrudes toward the hanging lead portion52, the minimum distance becomes smaller than the predetermined distanceL2 when the head end position A1 is aligned with the head end positionB1 of this embodiment. Therefore, the head end position B1 of the leadterminal portion 5 of this embodiment can be set at a more innerposition by a distance L3 in comparison with the head end position A1 ofthe conventional lead terminal portion 53. Since the lengths of the leadterminal portions 5, 53 are the predetermined length L1 respectively,the rear end position B2 of the lead terminal portion 5 of thisembodiment is at a more inner position in comparison with the rear endposition A2 of the conventional lead terminal portion 53. As a result, aunit region of such a lead frame 1 according to the present inventioncan be small-sized.

Further, since the sealing resin is formed substantially in the sameplane with the rear end positions A2, B2, a semiconductor device using alead frame 1 of this embodiment can be more small-sized by 2×L3 per oneside. Therefore, the packaging area of the semiconductor device can besmaller.

It is also noted that as can be seen in FIG. 2 (as well as in FIG. 1),the respective head sides of the successively adjacent lead terminalportions 5 confronting the semiconductor chip are aligned along astraight line (for example, line B1 in FIG. 2).

FIG. 4 is a schematic sectional view of a semiconductor devicefabricated using such a lead frame 1. Each part of the lead frame 1 isgiven with the same reference numeral as shown in FIG. 1 and thedescription thereof is omitted.

A semiconductor chip 6 is die-bonded on a supporting portion 4. Thesupporting portion 4 is X-shaped (see FIG. 1). The area of the uppersurface of the supporting portion 4 is smaller than that of the bottomsurface of the semiconductor chip 6.

Electrodes formed on the upper surface of the semiconductor chip 6 andthe lead terminal portions 5 are electrically connected to each other bymetal wires 7. The semiconductor chip 6, metal wires 7 and a part of thelead frame 1 are covered with a sealing resin 8. At the bottom surfaceof the semiconductor device, the lead terminal portions 5 and thesealing resin 8 are formed in the same plane, and the bottom surface ofeach lead terminal portion 5 is exposed. The sealing resin 8 is presentbelow the supporting portion 4 by a thickness corresponding to theheight of the upsetting. Further, the end face of the lead terminalportion 5 is substantially in the same plane with the side surface ofthe sealing resin 8.

A semiconductor device having such a structure can be surface-mounted,for example, on a wiring substrate with the lead terminal portions 5exposed at the bottom surface functioning as outer terminals. Further,since only one surface side of the lead terminal portion 5 is sealed bythe sealing resin 8, the thickness of the semiconductor device can bemade smaller. Therefore, such a semiconductor device can be suitablymounted on each kind of thin type apparatus.

The sealing resin 8 is present below the supporting portion 4, andtherefore, the supporting portion 4 and the hanging lead portion 3 arefirmly connected with the sealing resin 8. Since the area of thesupporting potion 4 is smaller than that of the bottom surface of thesemiconductor chip 6, parts of the bottom surface of the semiconductorchip 6 are in direct contact with the sealing resin 8. As a result,exfoliating phenomenon occurring at the boundary surface between thesupporting portion 4 and the semiconductor element 6 can be reduced.

Though one embodiment of the present invention has been described above,the present invention can be embodied in other forms. For example, inthe abovementioned embodiment, a lead terminal portion 5 having the wideportions and the narrow portions, but the lead terminal portion 5 mayhave the same width throughout the length thereof. Further, the wideportion of the lead terminal portion 5 has a section in the shape of aninverted trapezoid in the abovementioned embodiment, but the wideportion may have a rectangular section. Further, the narrow portion ofthe lead terminal portion 5 may have a section in the shape of aninverted trapezoid, and the lead terminal portion 5 may have the samesection in the shape of an inverted trapezoid throughout the lengththereof.

Further, in the abovementioned embodiment, the head end face of the leadterminal portion 5 is in the same plane with the side surface of thesealing resin 8, but the head end face of the lead terminal portion 5may covered with the sealing resin 8. Furthermore, the lead terminalportion 5 may be cut at a position protruding from the sealing resin 8.In this case, since the lead terminal portion 5 can be mounted on awiring substrate or the like at a position protruding from the sealingresin 8, the lower surface of the lead terminal portion 5 need not beexposed from the sealing resin 8.

Further, though the supporting portion 4 on which a semiconductor chip 6is die-bonded is X-shaped in the abovementioned embodiment, thesupporting portion 4 may be in other shapes such as a rectangle.

Further, though the supporting portion 4 is upset in the abovementionedembodiment, the present invention can include such structures that thesupporting portion 4 is in the same plane with the lead terminal portion5 and that the supporting portion 4 is downset at a position lower thanthe lead terminal portion 5.

Although the embodiments of the present invention has been described andillustrated in detail, it is clearly understood that the same is by wayof illustration and example only and is not to be taken by way oflimitation, the spirit and scope of the present invention being limitedonly by the terms of the appended claims.

This application corresponds to the Japanese Patent Application No.2000-307377 filed in the Japanese Patent Office on Oct. 6, 2000, and theentire disclosure of the Japanese application is incorporated herein byreference.

1. A semiconductor device, comprising: a semiconductor chip havingelectrodes on the surface thereof, a lead frame having a plurality oflead terminal portions for electrical connection, a supporting portionon which the semiconductor chip is mounted, and hanging lead portionsdisposed outside a region of the supporting portion and coupled to thesupporting portion, metal wires for connecting the lead terminalportions and the electrodes of the semiconductor chip to each other, anda sealing resin for sealing the semiconductor chip, the lead frame andthe metal wires in such a manner that a part of each lead terminalportion is exposed, each of the plurality of lead terminal portionshaving a first wide portion, a narrow portion and a second wide portionat shifted positions in a longitudinal direction thereof, the first wideportion being disposed closer to the semiconductor chip than the narrowportion, the second wide portion being disposed more remotely from thesemiconductor chip than the narrow portion, the plurality of leadterminal portions including adjacent pairs of said lead terminalportions, the first wide portions of each adjacent pair of lead terminalportions having adjacent sides which are parallel to each other, theplurality of lead terminal portions including a chamfered lead terminalportion disposed adjacent to the hanging lead portion, the first wideportion of the chamfered lead terminal portion being provided with achamfered portion formed substantially in parallel with the adjacenthanging lead portion, wherein each said lead terminal portion has anupper surface and a bottom surface, widths of the upper surfaces of thefirst and second wide portions being wider than a width of the uppersurface of the narrow portion, widths of the lower surfaces of the firstand second wide portions being equal to a width of the lower surface ofthe narrow portion, such that the first wide portion has an invertedtrapezoid-shaped cross-section and the narrow portion has arectangularly shaped cross-section, and the chamfered portion includes alinear side that is parallel to a lateral side of the hanging leadportion and the linear side of the chamfered portion extends acrosssubstantially an entire width of the second wide portion.
 2. Thesemiconductor device according to claim 1, wherein a side of the leadterminal portion includes a step between the first wide portion andnarrow portion.
 3. The semiconductor device according to claim 1,wherein the first wide portion and the narrow portion have respectivesections that are uniform in a longitudinal direction of the leadterminal portion.
 4. The semiconductor device according to claim 1,wherein the hanging lead portions each have a step, whereby thesupporting portion is offset from the lead terminal portions.
 5. Thesemiconductor device according to claim 1, wherein the plurality of leadterminal portions includes successively adjacent lead terminal portionswhose first wide portions each have a head side confronting thesemiconductor chip, the head sides of the respective successivelyadjacent lead terminal portions being aligned along a straight line. 6.A lead frame, comprising: a plurality of lead terminal portions forelectrical connection, a supporting portion for a semiconductor chip,and hanging lead portions disposed outside a region of the supportingportion and coupled to the supporting portion, each of the plurality oflead terminal portions having a first wide portion, a narrow portion anda second wide portion at shifted positions in a longitudinal directionthereof, the first wide portion being disposed closer to the supportingportion than the narrow portion, the second wide portion being disposedmore remotely from the supporting portion than the narrow portion, thefirst and second wide portions both being wider than the narrow portion,the plurality of lead terminal portions including adjacent pairs of saidlead terminal portions, the first wide portions of each adjacent pair oflead terminal portions having adjacent sides which are parallel to eachother, the plurality of lead terminal portions including a chamferedlead terminal portion disposed adjacent to the hanging lead portion, thefirst wide portion of the chamfered lead terminal portion being providedwith a chamfered portion formed substantially in parallel with theadjacent hanging lead portion, wherein each said lead terminal portionhas an upper surface and a bottom surface, widths of the upper surfacesof the first and second wide portions being wider than a width of theupper surface of the narrow portion, widths of the lower surfaces of thefirst and second wide portions being equal to a width of the lowersurface of the narrow portion, such that the first wide portion has aninverted trapezoid-shaped cross-section and the narrow portion has arectangularly shaped cross-section, and the chamfered portion includes alinear side that is parallel to a lateral side of the hanging leadportion and the linear side of the chamfered portion extends acrosssubstantially an entire width of the second wide portion.
 7. The leadframe according to claim 6, wherein a side of the lead terminal portionincludes a step between the first wide portion and narrow portion. 8.The lead frame according to claim 6, wherein the first wide portion andthe narrow portion have respective sections that are uniform in alongitudinal direction of the lead terminal portion.
 9. The lead frameaccording to claim 6, wherein the hanging lead portions each have astep, whereby the supporting portion is offset from the lead terminalportions.
 10. The lead frame according to claim 6, wherein the pluralityof lead terminal portions includes successively adjacent lead terminalportions whose first wide portions each have a head side confronting thesupporting portion, the head sides of the respective successivelyadjacent lead terminal portions being aligned along a straight line.